Current sensing technique is widely applied to various fields, such as motor monitoring, energy measuring, and the protection of lighting equipment and so on. Current sensing technique is mainly classified into two categories: intrusive current sensing technique and non-intrusive current sensing technique. The intrusive current sensing technique is to insert an additional element into current path of a device under test, so that the information of the current can be obtained from the voltage drop or the current induced due to the current change on the additional element.
Non-intrusive current sensing technique is not required to insert an additional element into current path of a device under test. It utilizes the magnetic effect of current to produce magnetic fields around a wire which current flows, and converts the magnetic fields to electrical signals with an element capable of sensing the magnetic fields.